1. Field of the Invention
This invention relates to an electronic telephone exchange and a method of connecting ports of the exchange, and more particularly to an electronic telephone exchange and a method of connecting ports of the exchange wherein an extension interface circuit adapted to connect such terminal device as a telephone set and an office line interface circuit adapted to connect an office line are removably connected through a connector.
2. Description of the Prior Art
As is well known in the art, the electronic telephone exchange is constituted by a time switch adapted to exchange connections bewween extensions and between an office line and an extension, a control device for controlling the exchange connection operation by the time switch, and interface circuits each connected to the highway of the time switch for exchanging communication signals between time switches of corresponding terminal devices through the highway.
For the users of such electronic telephone exchange, there are a case in which many extensions are necessary but the number of the office lines may be small and a case wherein a large number of the office lines are necessary but the number of the extensions may be small. Therefore, it is convenient to construct the telephone exchange such that the number of the extensions and the number of the office lines can be varied according to the needs of a user.
Consequently, a flexible port type electronic telephone exchange has been proposed in which each interface circuit connected to the highway of the time switch can be selectively used for the extension or the office line by changing the address number (port number) assigned to each interface circuit.
In the flexible type electronic telephone exchange, since the port number of the interface circuit is changed by software, there is a problem of complicating the software. Moreover, in a system wherein the port number is fixed, when it is desired to change the telephone system to the flexible port type, it is necessary to develop new software, which requires time and cost.